1. Field of the Invention
This invention relates to magnetic levitation transport systems, and more particularly to a magnetic levitation transport system having vehicles lifted by a magnetic force generating device which attracts magnetic members extending along a running track, and propelled by a linear motor to transport loads.
2. Description of the Related Art
A conventional magnetic levitation transport system will be described with reference to FIGS. 21 through 23. This system includes a load carrying vehicle A lifted and propelled along a guide rail B defining a running track in a cleanroom. The vehicle A is magnetically levitated, and driven by a linear motor to move from one loading and unloading station ST to another.
The guide rail B includes a main body B1 formed by extrusion molding a non-magnetic material such as aluminum. The main body B1 is in the shape of a square tube, with an upper surface defining an opening extending longitudinally of the rail B. The main body B1 has magnetic members 3 attached to lower sides of the upper surface. The magnetic members 3 extend along the upper opening and are spaced from each other transversely of the main body B1. The vehicle A has levitating electromagnets 2 disposed under and attracting the magnetic members 3, respectively. The vehicle A is movable along the guide rail B, with a main body A1 of the vehicle A disposed inside the main body B1 of the rail B. The guide rail B further includes primary coils 5 of a linear motor mounted in the bottom thereof.
As shown in FIG. 23, the primary coils 5 are arranged at intervals along the guide rail B to decelerate and stop the vehicle A at each station ST and to start and accelerate the vehicle A.
The main body B1 of the guide rail B contains stopping electromagnets 7 in positions opposed to each station ST. These electromagnets 7 attract, from below, stopping magnetic members 8 attached to the vehicle A to maintain the vehicle A at a standstill. The magnetic members 8 are arranged in the front and rear and fight and left comers of the vehicle A. Thus, four electromagnets 7 are arranged in place to act on the respective magnetic members 8.
The vehicle A includes a flat load supporting deck 15 disposed on top. The levitating electromagnets 2 are arranged in the front and rear and right and left comers of the vehicle A to act as magnetic force generating means for attracting the levitating magnetic members 3 from below. The vehicle A further includes a secondary conductor 6 formed of a non-magnetic material such as aluminum to act on the primary coils 5 of the guide rail B. The secondary conductor 6 is supported in horizontal posture in a lower region of the vehicle A, with a transversely middle position thereof attached to a prop 6b depending from a transversely middle position of the main body A1 of the vehicle A. The guide rail B supports magnetic plates 6c arranged only in positions where the primary coils 5 are present. The secondary conductor 6 is movable through spaces defined between the magnetic plates 6c and upper surfaces of the primary coils 5. Thrust is applied to the vehicle A when the secondary conductor 6 passes through these spaces.
The levitating electromagnets 2 are electrified by a battery 10 mounted on the main body A1 of the vehicle A. As a result, upper surfaces of the levitating electromagnets 2 are maintained within a predetermined range of distance from lower surfaces of the levitating magnetic members 3 based on information provided by gap sensors (not shown). The stopping electromagnets 7 are electrified only when maintaining the vehicle A at a standstill at the station ST.
In FIG. 21, reference W1 denotes guide rollers for maintaining vertical spacing between the levitating electromagnets 2 and magnetic members 3 when the electromagnets 2 are de-electrified. Reference W2 denotes guide rollers for maintaining a smaller transverse spacing between the vehicle A and guide rail B than a predetermined value, to prevent the vehicle A from colliding with inner lateral surfaces of the levitating magnetic members 3.
The known magnetic levitation transport system has the disadvantage of having to change or charge the battery 10 every five to six hours, which impairs operating efficiency of the vehicle A. Moreover, the battery 10 must be subjected to maintenance periodically.
In order to overcome these disadvantages, it is conceivable to lay along the guide rail B a power rail formed of a conductive material such as copper, and provide the vehicle A with a collector to contact and receive power from the power rail to charge the battery 10. With such a construction, however, maintenance is imperative since the power rail and collector become worn through contact. Further, this construction would produce wastes such as abrasion dust, and cannot therefore be used in a cleanroom.